The literature describes coating methods wherein mixtures of EC (ethylcellulose) and HPMC (hydroxypropyl methylcellulose) are applied on spherical granules. Spherical granules comprising an active pharmaceutical ingredient (API) are conventionally obtained by spheronisation, including a spheronisation aid in the granules, or by coating non-pareil particles with API. The known methods are limited to be used for spherical granulate in order to reproducibly obtain a specific release profile.
There exists 250 mg PENTASA capsules on the US market. The capsules comprise a mixture of spherical pellets with a drug load of 66% mesalazine and non-pareil pellets. The mesalazine pellets are coated with an about 12 μm thick coating of EC, HPMC and acetylated monoglyceride. The capsule exhibits an approximately zero order release profile.
EP 540 813 A1 describes coating of spherical pellets comprising acetazolamide with a mixture of a water-insoluble film former such as ethylcellulose and a water-soluble film former such as hydroxypropyl methylcellulose to form a coating.
GB 2 163 957 A describes coating of pellets comprising theophylline with a mixture of ethylcellulose, hydroxypropyl methylcellulose and di-n-butylphthalate in a solvent comprising isopropanol, ethanol and water. The size of the pellets is defined by a diameter.
U.S. Pat. No. 5,188,841 describes spherical pellets coated with ethylcellulose and hydroxypropyl methylcellulose to obtain a modified release formulation. In vitro tests show an extended, approximately linear release rate for ketoprofen at typical physiological pH values.
There exists a need for a low-cost, reproducible method for coating granules irrespective of their shape or of irregular shapes on an industrial scale.
The present invention provides a coating method applicable for granulate independent on the shape of the granulate. It is especially suited for oblong or cylindric granulate obtained directly from an extruder. It provides a simple, cost-effective method for obtaining a controllable, e.g. a zero order, reproducible release profile on an industrial scale. The method has surprisingly shown to be suitable for an extruded mesalazine product, even with a high drug load.